Which of these techniques allows us to determine whether or not an organic molecule contains conjugation (a sequence of alternating single and double (or triple) bonds?Group of answer choicesUV/Vis spectroscopy1H NMR spectroscopycombustion analysismass spectrometryIR spectroscopy

The technique that allows us to determine whether or not an organic molecule contains conjugation (a sequence of alternating single and double or triple bonds) is UV/Vis Spectroscopy.

UV/Vis spectroscopy measures the absorption of light in the ultraviolet and visible ranges. Molecules with conjugated systems have pi electrons that can absorb energy from light in these ranges, causing electronic transitions. The specific wavelengths absorbed can provide information about the extent of conjugation in the molecule.

The other techniques listed (1H NMR spectroscopy, combustion analysis, mass spectrometry, IR spectroscopy) provide different types of information:

• 1H NMR spectroscopy provides information about the number and type of hydrogen atoms in a molecule.
• Combustion analysis provides information about the amount of carbon, hydrogen, and oxygen in a compound, which can be used to determine the empirical formula.
• Mass spectrometry provides information about the molecular weight of the compound and its structure.
• IR spectroscopy provides information about the functional groups present in a molecule.